Search Images Maps Play YouTube News Gmail Drive More »
Sign in
Screen reader users: click this link for accessible mode. Accessible mode has the same essential features but works better with your reader.

Patents

  1. Advanced Patent Search
Publication numberUS5289069 A
Publication typeGrant
Application numberUS 07/748,937
Publication dateFeb 22, 1994
Filing dateAug 23, 1991
Priority dateAug 29, 1990
Fee statusPaid
Also published asDE69107941D1, DE69107941T2, EP0478142A1, EP0478142B1
Publication number07748937, 748937, US 5289069 A, US 5289069A, US-A-5289069, US5289069 A, US5289069A
InventorsMakoto Hasegawa, Kenji Kubo, Naoto Noguchi, Toshio Imai
Original AssigneeMatsushita Electric Industrial Co., Ltd.
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Brushless motor
US 5289069 A
Abstract
A brushless motor comprises a rotor which is rotatable on an axis of the brushless motor and which include permanent magnets arranged circumferentially thereon, an output member connected to the rotor to rotate with the rotor, and a stator which includes electro-magnetic coils energized in order to rotate the rotor, and has a first space which receives the output member therein and a second space which extends from the first space to the outside of the stator so that an output power of the brushless motor is transmitted from the output member to the outside of the brushless motor through the second space.
Images(8)
Previous page
Next page
Claims(15)
What is claimed is:
1. A brushless motor comprising:
rotor means which is rotatable on an axis of the brushless motor and which includes permanent magnets arranged circumferentially thereon,
output means connected to the rotor means to rotate with the rotor means, and
stator means which includes electro-magnetic coils energized in order to rotate the rotor means, said stator means having a first space which receives the output means therein and a second space which extends radially from the first space to a region external to the stator means so that an output power of the brushless motor is transmitted from the output means to a region external to the brushless motor through the second space,
the rotor means comprising sub-rotor means which is rotatable on the axis of the brushless motor, the sub-rotor means being fixed to the output means and having permanent magnets whose N poles face S poles of the rotor means through the second space and whose S poles face N poles of the rotor means through the second space.
2. A brushless motor according to claim 1, wherein the N poles of the permanent magnets of the sub-rotor means face the S poles of the rotor means through the stator means and wherein the S poles of the permanent magnets of the sub-rotor means face the N poles of the rotor means through the stator means.
3. A brushless motor according to claim 1, wherein the sub-rotor means includes a magnetically conductive material.
4. A brushless motor according to claim 1, wherein the second space extends substantially perpendicularly to the axis of the brushless motor.
5. A brushless motor according to claim 1, wherein the output means is a pulley.
6. A brushless motor according to claim 1, wherein the output means is a gear.
7. A brushless motor according to claim 1, wherein the electro-magnetic coils of the stator means are made by an etching process.
8. A brushless motor according to claim 1, wherein the electro-magnetic coils of the stator means are made by a plating process.
9. A brushless motor according to claim 1, wherein a number of coil turns of the electro-magnetic coils energized simultaneously is always constant.
10. A brushless motor according to claim 2, wherein a magnetomotive force of the permanent magnets of the sub-rotor means is substantially equal to that of the rotor means.
11. A brushless motor according to claim 7, wherein the electro-magnetic coils of the stator means are covered by an electric insulating material to fix securely the electro-magnetic coils to the stator means.
12. A brushless motor according to claim 10, wherein an axial magnetically energized clearance between the permanent magnets of the sub-rotor means and the electro-magnetic coils of the stator means is substantially equivalent to an axial magnetically energized clearance between the permanent magnets of the rotor means and the electro-magnetic coils of the stator means.
13. A brushless motor according to claim 3, wherein an axial magnetically energized clearance between the sub-rotor means and the electro-magnetic coils of the stator means is substantially equivalent to an axial magnetically energized clearance between the rotor means and the electro-magnetic coils of the stator means.
14. A brushless motor according to claim 8, wherein the electro-magnetic coils of the stator means are covered by an electric insulating material to fix securely the electro-magnetic coils to the stator means.
15. A brushless motor according to claim 1, wherein the electro-magnetic coils adjacent to each other do not overlap each other in an axial direction of the brushless motor.
Description
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT

The present invention relates to a brushless motor, particularly relates to a flat brushless motor with a short axial length preferable for a compact electric device.

As shown in FIG. 12, a conventional brushless motor used in the compact tape recorder has a body 101 receiving a stator coil, a rotor including permanent magnets and a sub-rotor. A rotor shaft 102 projects axially outwardly from the body 101, and a pulley 103 is mounted on the rotor shaft 102 at the outside of the body 101 so that an output power of the brushless motor can be transmitted by a belt 104 wound on the pulley 103.

OBJECT AND SUMMARY OF THE INVENTION

An object of the present invention is to provide a brushless motor which has a small axial length although the brushless motor has output means for transmitting an output power of the brushless motor to the outside of the brushless motor.

According to the present invention, a brushless motor comprises,

rotor means which is rotatable on an axis of the brushless motor and which include permanent magnets arranged circumferentially thereon,

output means connected to the rotor means to rotate with the rotor means, and

stator means which include electro-magnetic coils energized in order to rotate the rotor means, and have a first space which receives the output means therein and a second space which extends from the first space to the outside of the stator means so that an output power of the brushless motor is transmitted from the output means to the outside of the brushless motor through the second space.

Since the stator means have the first space which receives the output means therein and the second space which extends from the first space to the outside of the stator means so that the output power of the brushless motor is transmitted form the output means to the outside of the brushless motor through the second space, a distance in the axial direction of the brushless motor between the stator means and the output means is substantially zero, a distance in the axial direction of the brushless motor between the output means and the rotor means is very small, and a distance in the axial direction of the brushless motor between the output means and a magnetically energized field between the stator means and the rotor means is very small. Therefore, a length of the brushless motor in the axial direction of the brushless motor is very small, and a difference in axial position between a force transmitted from the output means to the outside of the brushless motor through the second space and a force generated on the rotor means by the stator means to drive the output means is very small so that a capacity of a bearing for supporting rotatably the rotor means and the output means in relation to the stator and for keeping accurately a space of the magnetically energized field between the stator means and the rotor means may be small.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view taken along a line 1--1 of FIG. 2 to show an embodiment of a flat brushless motor according to the present invention.

FIG. 2 is a front view showing the embodiment of FIG. 1.

FIG. 3 is a side view showing the embodiment of FIG. 1.

FIG. 4 is a front view showing an embodiment of a stator according to the present invention.

FIG. 5 is a schematic front view showing an arrangement of permanent magnets on a rotor.

FIG. 6 is a front view showing an arrangement of the stator, the rotor and a pulley.

FIG. 7 is a front view showing an arrangement of the rotor and the pulley.

FIG. 8 is a diagram showing a control device for energizing in order electro-magnets of the stator.

FIG. 9 is a schematic view showing a structure for mounting the stator and terminal members of the stator.

FIG. 10 is a cross-sectional view showing another embodiment of the present invention.

FIG. 11 is a cross-sectional view showing another embodiment of the present invention.

FIG. 12 is a side view showing a conventional brushless motor.

FIG. 13 is a front view showing an arrangement of the stator, the rotor and a gear.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

As shown in FIGS. 1 to 7, an embodiment of a flat brushless motor according to the present invention includes a stator 1 containing electro-magnet driving coils 1a. An outer periphery of the stator 1 has a terminal holding member lb including terminals 1c, and a first space 1d of the stator 1 is formed at a central portion of the stator 1. As shown in FIG. 4, the driving coils 1a (FIG. 6) constituted by individual coils L1a, L1b, L2a, L2b, L3a and L3b (FIG. 4) whose coil turns may be substantially equal to each other to form respective magnetic flux densities identical to each other are arranged on a circular line separately with angular distances of 40 degrees. Alternatively, a total amount of coil turns of L1a and L1b, a total amount of coil turns of individual coils L2a and L2b, and a total amount of coil turns of individual coils L3a and L3b may be equal to each other so that the respective magnetic flux densities of three-phases magnetic energizing are equal to each other. Three-phase driving combinations of individual coils L1a-L1b, L2a-L2b and L3a-L3b are energized in order so that a magnetically energized field by the driving coils 1a rotates along the circular line. A second space 1e of the stator 1 is formed between individual coils L1a and L3b (FIG. 4). Each of the three-phases driving combinations has the same number of the driving coils 1a, that is, two of the driving coils 1a so that driving forces by the three-phases driving combinations of the driving coils la are substantially equal to each other. Therefore, a driving force by the driving coils la is always constant. In a preferred embodiment, as clearly seen in FIG. 4, the electromagnetic coils adjacent to each other do not overlap each other in the axial direction of the brushless motor.

A disk-shaped rotor 2 is rotatable on an axis of the brushless motor and has permanent magnets 2a facing to the driving coils 1a of the stator 1 with an axial magnetically energized clearance therebetween. A number of poles of the permanent magnets 2a is twelve and the permanent magnets 2a are arranged on the rotor 2 with angular distances of 30 degrees, as shown in FIG. 5. A pulley 2b is fixed to the rotor 2 and a central axis of the pulley 2b is kept on that of the rotor 2. The pulley 2b is mounted on a shaft 2c so that the pulley 2b is rotatably supported through the shaft 2c by a bearing 3a fixed to a bracket 3. The pulley 2b has a V-shaped belt groove 2d at an outer periphery thereof, and has a cylindrical projection 2e.

The bearing 3a has a radial bearing 3b and a thrust bearing 3c. The bracket 3 has a magnetic shield plate 3d which is made of a magnetically conductive material and extends along an outer periphery of the brushless motor so that an electromagnetic wave generated by the stator 1 is prevented from acting on an electronic device, for example, a tuner circuit or amplifier circuit or a magnetic head. The stator 1 is supported on the bracket 3 through a plurality of support columns 3e by screws 6.

A sub-rotor 4 is fixed to the pulley 2b through a holder member 4b fixed to the projection 2e of the pulley 2b so that the sub-rotor 4 and the rotor 2 are rotatable on the axis of the brushless motor. The sub-rotor 4 has permanent magnets 4a which are the same as the permanent magnets 2a and face the driving coils 1a of the stator 1 with an axial magnetically energized clearance therebetween so that the stator 1 is arranged between the sub-rotor 4 and the rotor 2. N poles of the rotor 2 face S poles of the sub-rotor 4 through the stator 1, and S poles of the rotor 2 face N poles of the sub-rotor 4 through the stator 1. From the above description and FIGS. 1 and 4, it will be immediately apparent that the N poles of the rotor 2 must necessarily face the S poles of the sub-rotor 4 through the second space 1e and similarly that the S poles of the rotor 2 must necessarily face the N poles of the sub-rotor 4 through the second space 1e. The holder member 4b extends radially outwardly from the projection 2e of the pulley 2b so that a diameter of the first space 1d is small although an inner diameter of the sub-rotor 4 is large. The magnetically energized clearance between the permanent magnets 4a of the sub-rotor 4 and the driving coils 1a of the stator 1 is substantially equal to the magnetically energized clearance between the permanent magnets 2a of the rotor 2 and the driving coils 1a of the stator 1 so that a magnetic force in an axial direction of the brushless motor between the sub-rotor 4 and the stator 1 is substantially equal to a magnetic force in the axial direction of the brushless motor between the rotor 2 and the stator 1. Therefore, a force in the axial direction of the brushless motor is not applied to the stator 1 and a movement or deformation of the stator 1 in the axial direction of the brushless motor is prevented. If a magnetomotive force of the permanent magnets 4a is different from that of the permanent magnets 2a, the magnetically energized clearance between the sub-rotor 4 and the stator 1 and the magnetically energized clearance between the rotor 2 and the stator 1 is adjusted to make the magnetic force in the axial direction between the sub-rotor 4 and the stator 1 substantially equal to the magnetic force in the axial direction between the rotor 2 and the stator 1. That is, when the magneto-motive force of the permanent magnets 4 a is smaller than that of the permanent magnets 2a, the magnetically energized clearance between the sub-rotor 4 and the stator 1 is made smaller than the magnetically energized clearance between the rotor 2 and the stator 1 so that a magnetic flux density by the permanent magnets 2a is made substantially equal to a magnetic flux density by the permanent magnets 4a, and when the magnetomotive force of the permanent magnets 4a is larger than that of the permanent magnets 2a, the magnetically energized clearance between the sub-rotor 4 and the stator 1 is larger than the magnetically energized clearance between the rotor 2 and the stator 1 so that a magnetic flux density by the permanent magnets 2a is made substantially equal to a magnetic flux density by the permanent magnets 4a.

A belt 5 is wound on the belt groove 2d of the pulley 2b in the first space 1d and passes through the second space 1e so that an output power of the brushless motor can be taken out to the outside of the brushless motor. A gear 12 (FIG. 13) may be fixed to the rotor 2 instead of the pulley 2b and may engage with another gear (not shown) which is rotatable on an axis at the outside of the brushless motor and is arranged in the second space 1e so that the output power of the brushless motor can be taken out to the outside of the brushless motor through the second space 1e, as shown in FIG. 6, although the pulley 2b or the gear 12 is received in the stator 1. Since the pulley 2b or the gear 12 for transmitting the output power of the brushless motor to the outside of the brushless motor is received in the stator 1, a size of the brushless motor, particularly an axial length of the brushless motor is small, and a moment which is generated by the pulley 2b or the gear 12 for transmitting the output power of the brushless motor to the outside of the brushless motor and by the stator 1 for driving the rotor 2 and/or the sub-rotor 4 and which is born by the bearing 3a is small.

As shown in FIG. 8, the coils L1a and L1b are connected to a terminal 1c1 in series, the coils L2a and L2b are connected to a terminal 1c2 in series, the coils L3a and L3b are connected to a terminal 1c3 in series, and the combinations of the coils L1a-L1b, L2a-L2b and L3a-L3b are connected together to a terminal 1c4 so that the three-phases driving combinations of L1a-L1b, L2a-L2b and L3a-L3b are energized in order by a control circuit 7 to rotate the rotor 2 and/or the sub-rotor 4. As shown in FIG. 9, since the terminals 1c of the stator 1 project outwardly from the terminal holder member 1b, the stator 1 can be easily connected to a printed circuit plate 8.

As shown in FIG. 10, a sub-rotor 11 includes permanent magnets 11a which are the same as the permanent magnets 2a or 4a with the twelve magnetic poles, and may be directly fixed to the projection 2e of the pulley 2b on the rotor 2 without the holder member 4b through a central recess 11b of the sub-rotor 11. A depth of the recess 11b is determined in such a manner that a magnetically energized clearance between the sub-rotor 11 and the stator 1 is substantially equal to the magnetically energized clearance between the rotor 2 and the stator 1. An inner diameter of an opening of the recess 11b is equal to that of the holder member 4b so that the sub-rotor 4 can be easily exchanged for the sub-rotor 11. N poles of the rotor 2 face to S poles of the sub-rotor 11 through the stator 1, and S poles of the rotor 2 face to N poles of the sub-rotor 11 through the stator 1 so that the sub-rotor 4 and the rotor 2 is rotated in accordance with changes of energizing the coils 1a of the stator 1.

As shown in FIG. 11, the sub-rotor 4 with the permanent magnets 4a may be replaced by a flat sub-rotor 12 made of a magnetically conductive material, for example, iron. The sub-rotor 12 is fixed to the projection 2e of the pulley 2b on the rotor 2 without the holder member 4b. An inner diameter of an opening of the sub-rotor 12 is equal to that of the holder member 4b so that the sub-rotor 4 can be easily exchanged for the sub-rotor 12 or each of the other various sub-rotors including a common opening diameter A magnetically energized clearance between the sub-rotor 12 and the stator 1 is substantially equal to the magnetically energized clearance between the permanent magnets 2a of the rotor 2 and the stator 1.

The coils 1a may be made by an etching process or by a plating process, and the sheet shaped coils 1a made on a surface of the stator 1 by an etching process or by a plating process may be securely fixed to the surface of the stator 1 by an electric insulating material covering the sheet-shaped coils 1a.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US3375385 *Feb 4, 1965Mar 26, 1968Gen Motors CorpRotor means connection
US4185215 *May 11, 1978Jan 22, 1980General Scanning, Inc.Permanent magnet synchronous motor
US4318017 *Jan 4, 1980Mar 2, 1982Timex CorporationRotor assembly for electric stepping motor
US4451749 *Aug 25, 1982May 29, 1984Nippondenso Co., Ltd.AC Generator
US4536672 *Aug 6, 1984Aug 20, 1985Nippondenso Co., Ltd.Flat type rotary electric machine
US4804574 *Feb 12, 1987Feb 14, 1989Sony CorporationLaminated printed coil structure
US4839551 *Mar 25, 1988Jun 13, 1989Alps Electric Co., Ltd.Brushless motor structure enabling accurate relative positioning of rotor and stator coils
US4987333 *Mar 16, 1990Jan 22, 1991Matsushita Electric Industrial Co., Ltd.Electric motor with inner drive pulley
US5028827 *Jul 16, 1990Jul 2, 1991Moesslacher HannesDrive unit comprising an electric motor
US5028829 *Oct 9, 1990Jul 2, 1991Papst-Motoren Gmbh & Co. K.G.Compact motor mount for cassette drive
EP0388965A2 *Mar 22, 1990Sep 26, 1990Matsushita Electric Industrial Co., Ltd.Brushless electric motor
JPS6225859A * Title not available
JPS60237845A * Title not available
JPS61236352A * Title not available
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US5392176 *Jul 26, 1993Feb 21, 1995Hewlett-Packard CompanyRecording/reproducing device employing device housing and printed circuit board and electronics as structural and functional part of media drive motor and the media drive motor
US5510664 *Sep 7, 1993Apr 23, 1996Ricoh Company, Ltd.Brushless motor
US5665944 *Jun 28, 1994Sep 9, 1997Kone OyElevator machinery
US5677585 *Jan 18, 1996Oct 14, 1997Sony CorporationMotor
US5783895 *Apr 3, 1995Jul 21, 1998Kone OyElevator motor with flat construction
US5837948 *Mar 6, 1997Nov 17, 1998Kone OyElevator machinery
US5945766 *Jan 16, 1997Aug 31, 1999Amotron Co., Ltd.Coreless-type BLDC motor and method of producing stator assembly having axial vibration attenuation arrangement
US5962948 *Jun 26, 1997Oct 5, 1999Kone OyElevator motor with flat construction
US5996742 *Nov 20, 1997Dec 7, 1999Kone OyElevator machinery
US6707207 *Dec 19, 2002Mar 16, 2004Hitachi Global Storage Technologies Netherlands B.V.High bandwidth track following actuator for hard disk drives
US6737778 *Sep 14, 2001May 18, 2004Mitsubishi Denki Kabushiki KaishaPulley driving system
US6794783Jan 13, 2003Sep 21, 2004Sunyen Co., Ltd.Flat rotary electric generator
US6943473 *Aug 19, 2003Sep 13, 2005Nissan Motor Co., Ltd.Electric rotating machine
US7036205Feb 25, 2003May 2, 2006Matsushita Electric Industrial Co., Ltd.Method of manufacturing stator for brushless motors
US7402934 *Aug 18, 2005Jul 22, 2008Revolution Motor Company, Inc.High performance air core motor-generator winding
US7525228 *Dec 29, 2006Apr 28, 2009Delta Electronics, Inc.Three-phase opposite rotating motor and fan
US8448751 *Apr 4, 2006May 28, 2013Otis Elevator CompanyElevator door system
CN1038027C *Jun 28, 1994Apr 15, 1998科恩股份公司Elevator machinery
Classifications
U.S. Classification310/156.37, 310/114, 310/179, 310/45, 310/83, 310/268
International ClassificationH02K29/00, H02K41/02, H02K7/10, H02K7/16, H02K7/14
Cooperative ClassificationH02K7/14, H02K7/1004, H02K7/16, H02K41/02
European ClassificationH02K41/02, H02K7/14, H02K7/16, H02K7/10B
Legal Events
DateCodeEventDescription
Jun 15, 2010ASAssignment
Owner name: MINEBEA MOTOR MANUFACTURING CORPORATION,JAPAN
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:PANASONIC CORPORATION (FORMERLY MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.;REEL/FRAME:24529/456
Effective date: 20100527
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:PANASONIC CORPORATION (FORMERLY MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.;REEL/FRAME:024529/0456
Jul 27, 2005FPAYFee payment
Year of fee payment: 12
Aug 2, 2001FPAYFee payment
Year of fee payment: 8
Aug 11, 1997FPAYFee payment
Year of fee payment: 4
Oct 23, 1991ASAssignment
Owner name: MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD. A CORPOR
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNORS:HASEGAWA, MAKOTO;KUBO, KENJI;NOGUCHI, NAOTO;AND OTHERS;REEL/FRAME:005894/0016
Effective date: 19910925